package top.chenbn.guli.util;

import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Random;

/**
 * @author chbn
 * @create 2020-07-16 12:35
 */
public class RandomUtil {
  private static final Random random = new Random();
  private static final DecimalFormat fourdf = new DecimalFormat("0000");
  private static final DecimalFormat sixdf = new DecimalFormat("000000");

  public static String getFourBitRandom() {
    return fourdf.format(random.nextInt(10000));
  }

  public static String getSixBitRandom() {
    return sixdf.format(random.nextInt(1000000));
  }
  /**
   * 给定数组，抽取n个数据
   *
   * @param list
   * @param n
   * @return
   */
  public static ArrayList getRandom(List list, int n) {
    Random random = new Random();
    HashMap<Object, Object> hashMap = new HashMap<Object, Object>();
    // 生成随机数字并存入HashMap
    for (int i = 0; i < list.size(); i++) {
      int number = random.nextInt(100) + 1;
      hashMap.put(number, i);
    }
    // 从HashMap导入数组
    Object[] robjs = hashMap.values().toArray();
    ArrayList r = new ArrayList();
    // 遍历数组并打印数据
    for (int i = 0; i < n; i++) {
      r.add(list.get((int) robjs[i]));
      System.out.print(list.get((int) robjs[i]) + "\t");
    }
    System.out.print("\n");
    return r;
  }
}
